Metal carboxylate additives for thermoplastics

Abstract

A thermoplastic composition includes a polyolefin having a polymeric backbone and, associated therewith, one or more ionic compounds having a central metal element and one or more carboxylic acid functional moieties. The thermoplastic composition may be, for example, polyethylene or polypropylene. A method of improving the mechanical properties of thermoplastics includes adding, to a thermoplastic composition having a polymeric backbone, an additive including one or more ionic compounds having a central metal element and one or more carboxylic acid functional moieties, wherein the additive is added to the thermoplastic composition at conditions suitable to associate the one or more ionic compounds to the polymeric backbone. The ionic compounds may be, for example, zinc cinnamate, zinc hydrocinnamate, zinc naphthoate, zinc naphthalene acetate, isophthalic acid zinc salt, and phthalic acid zinc salt, and their equivalents substituting calcium or magnesium instead of zinc as the central metal element, and mixtures thereof.

Description

FIELD OF THE INVENTION[0001]This invention relates to metal carboxylate additives for thermoplastics which impart improved mechanical properties, including, for example, heat distortion temperature, modulus, and tensile strength. More particularly, the invention relates to thermoplastics, such as polyolefins, which include additive compositions for imparting improved mechanical properties. Additionally, this invention relates to the methods for imparting improved mechanical properties to thermoplastics, the resulting enhanced thermoplastics and articles.BACKGROUND OF THE INVENTION[0002]In many industrial applications, formulated thermoplastic compositions require a balance of cost and performance. To that end, commodity materials such as polyethylene and polypropylene are attractive suitors from a cost standpoint, but are deficient in heat distortion temperature, modulus or tensile strength (herein referred to as mechanical properties). Classical efforts to improve the mechanical pr...

AI Technical Summary

Benefits of technology

The patent is about a discovery that adding certain metal salts to thermoplastics makes them stronger and more durable. This can be done by simply adding the metal salt to the thermoplastic. The metal salts interact with the thermoplastic, making it more robust without needing further treatment or additional processing steps. This means that thermoplastics can now be made with better mechanical properties, similar to those of crosslinked, reinforced, or nucleated thermoplastics. The process can be used with a wide range of thermoplastics, specifically polyolefins such as polyethylene and polypropylene.

Problems solved by technology

In many industrial applications, formulated thermoplastic compositions require a balance of cost and performance.

To that end, commodity materials such as polyethylene and polypropylene are attractive suitors from a cost standpoint, but are deficient in heat distortion temperature, modulus or tensile strength (herein referred to as mechanical properties).

Classical efforts to improve the mechanical properties, such as glass reinforcement, will often result in deterioration of other beneficial properties.

Additionally, known methods to improve the mechanical properties of thermoplastics often require substantial deviation in process operations and material requirements.

Polyolefins, however, do not possess the thermal characteristics to compete against engineered thermoplastics.

Some advances have been developed which overcome this deficiency to some degree, but generally the beneficial properties listed above are diminished.

Other desirable properties, however, are diminished by the inclusion of such additives.

Known methods for improving the mechanical properties of thermoplastics have focused on chemical modifications to the structure of the thermoplastic, changes to the crystallization characteristics of the thermoplastic, or crosslinking the thermoplastic composition, all of which require additional processes and equipment which can increase the operational costs for production of mechanically robust thermoplastics.

Such reinforced thermoplastics may offer the desired mechanical properties, but they require additional materials which can increase the cost of production.

As mentioned above, these methods also often reduce the native properties of the thermoplastics, such as flowability, proccessability, ease of conversion, and specific gravity.

As a result, while certain mechanical properties are improved by this process, other desirable properties are sacrificed or lost.

However, the process is cumbersome and difficult to control in conventional compounding equipment.

Additionally, the final composition is deemed a thermoset and is not reprocessible, a desirable characteristic of polyolefins.

One deficiency of this technology is that is that is not effective with more rapid crystallizing polyolefins, such as the polyethylene family.

Additionally, the use of metal salts as nucleators, and the resulting nucleation of the thermoplastic, requires additional materials which can increase the cost of production.

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